Neuroscience explained by a neuroscientist (and pianist, composer, and advocate)

Introduction

Let me say that again, Drug Addiction is a medical disease-a disease of the brain.

To some people, this may sound controversial but throughout my posts I hope to provide the scientific explanation for why this is and how we know that this is true. Drug addiction is a very complex disease and a great deal of knowledge is required to understand it.

But what is addiction? The textbook definition of addiction (according to Wikipedia) is “a state characterized by compulsive engagement in rewarding stimuli, despite adverse consequences”. “Rewarding stimuli” can be food, sex, gambling, the Internet, or in our case, drugs of abuse. And as we’ll learn later, all these “rewarding stimuli” hijack the brain in very similar (yet distinct) ways. “Adverse consequences” can be anything from losing your job to deterioration of your health to committing a crime.

Historically, a drug addict was considered someone that was weak, lacked a strong will, or was morally inferior. This is not true.

Drugs of abuse (nicotine, cocaine, marijuana, alcohol, heroin, oxycodone, etc.) are not magic: they are physical substances that have a physical effect, specifically on the brain. The function of an addict’s brain has been changed as a result of the drug use; their behaviors and motivations—even what you might call their “will—have changed (more on this later). An addict is not “morally weak” but suffering from an illness of the brain and, in many instances, in need of compassion and help.

A quick note:

I must point out that a person cannot even become a drug addict unless they try the drug in the first place. But the reasons behind this first use are complicated with numerous contributing factors to consider: sociology, public policy, genetic predisposition, environment, and many other issues. Ridiculous simplifications such as “just say no” or absurd taglines like “the war on drugs” don’t even begin to address the problem. More on this in future posts.

Another quick note: This post is a bit long but I will try to keep future ones a more reasonable length.

Now, back to the neuroscience:

By now, some of the questions you should be asking are: how do we know that addiction is a medical disease/brain disease? How do drugs act on the brain and what do we even mean that brain function is “changed”? And even if drugs do change the brain, how does this translate into changed behavior, such as uncontrollable drug craving, or bad behavior/“adverse consequences”?

So we all know that our body is made up of organs: heart, lungs, intestines, etc. and those organs are responsible for carrying out different jobs that keep us alive (blood circulation, breathing, food digestion and absorption, etc.). The brain is an organ just like any other with specific jobs to do.

We were taught since we were young that the brain is the control center of the body, which is one of those phrases that is technically true but doesn’t really offer much real insight. By control center, we mean that the brain controls, regulates, and coordinates how our organs function (breathing, heart rate, muscle movement, etc.). Less well understood is that the brain also controls our behaviors, actions, thoughts, and emotions—our minds.

Let me phrase that in a different way, the result of the brain’s functions IS the mind!

This may be controversial to some and at the neuroscientific level, is remarkably complex and not very intuitive. The brain vs mind topic will be a primary theme this blog will cover.

But let’s just assume for a moment that I’m correct and our thoughts and behaviors come from the biological functions of the brain. Then if something changes how the brain operates (like an illegal drug, for example), then it stands to reason our thoughts and behaviors would also be changed. If this change is harmful and results in negative behaviors or thoughts, you could think of the brain as suffering from a disease.

Let’s consider this in slightly more detail by thinking about disease more generally.

You may or may not have thought about this in this way, but the entire modern medical profession is based on a standard way of treating illness: the medical model of disease. The model is simple to understand: illness occurs because something (bacteria, virus, a genetic mutation, a poison, etc.) affects a particular organ, causing it to not work properly and resulting in the symptoms of the disease. Therefore, if you eliminate the cause of, or reverse, the damage to the organ, you ameliorate the symptoms and cure the disease.

The figure below compares three different diseases in the context of the disease model: cystic fibrosis, hepatitis, and drug addiction.

For cystic fibrosis, the cause of the disease is a genetic mutation that you inherit from your parents. The organ the mutation affects is the lung. The mutation causes the lungs to produce more mucous which makes breathing more difficult (the symptoms).

For hepatitis, a virus, the hepatitis virus, causes the disease. The virus specifically infects the liver (the affected organ), which it damages and causes a loss of appetite and malaise, can lead to yellow discoloration of the skin, or more severe liver damage (the symptoms).

For drug addiction, the cause of the disease is drug abuse. The drugs act on brain cells (neurons) which changes how they work. The change in brain function results in the drug-specific effects that you experience right away, while repeated use results in cravings, drug-seeking behavior, and even withdrawals (all of these are symptoms).

However, unlike the other diseases, the symptoms of cystic fibrosis or hepatitis do not feedback onto the organ to worsen the effects of the initial cause. But for drug addiction, this is exactly what happens. Drug addiction operates in a cycle in which the symptoms promote the cause (more on this in the future).

And one more significant caveat, not everyone that tries a drug will become an addict. This is just another layer of complexity that will be discussed in more detail later.

But so far, I haven’t discussed any concrete neuroscience. I’ve kept things very vague with phrases like “changes in brain function” but what changes am I talking about? Specifically, drugs change how brain cells, called neurons, talk to one another.